This invention relates generally to magnetic disk data storage systems, and more particularly to magnetic write heads and methods for making same.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1A and 1B, a magnetic disk data storage systems 10 of the prior art includes a sealed enclosure 12, a disk drive motor 14, a magnetic disk 16, supported for rotation by a drive spindle S1 of motor 14, an actuator 18 and an arm 20 attached to an actuator spindle S2 of actuator 18. A suspension 22 is coupled at one end to the arm 20, and at its other end to a read/write head or transducer 24. The transducer 24 (which will be described in greater detail with reference to FIG. 1C) typically includes an inductive write element with a sensor read element. As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the transducer 24 causing it to lift slightly off of the surface of the magnetic disk 16, or, as it is termed in the art, to "fly" above the magnetic disk 16. Alternatively, some transducers, known as "contact heads," ride on the disk surface. Various magnetic "tracks" of information can be written to and/or read from the magnetic disk 16 as the actuator 18 causes the transducer 24 to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
FIG. 1C depicts a magnetic read/write head 24 including a read element 26 and a write element 28. The edges of the read element 26 and write element 28 also define an air bearing surface ABS, in a plane 29, which faces the surface of the magnetic disk 16.
The read element 26 includes a first shield 30, an intermediate layer 32, which functions as a second shield, and a read sensor 34 that is located between the first shield 30 and the second shield 32. The most common type of read sensor 34 used in the read/write head 24 is the magnetoresistive (MR or GMR) sensor which is used to detect magnetic field signals from a magnetic medium through changing resistance in the read sensor.
The write element 28 is typically an inductive write element. The write element 28 includes the intermediate layer 32, which functions as a first pole, and a second pole 38 disposed above the first pole 32. The first pole 32 and the second pole 38 are attached to each other by a backgap portion 40, with these three elements collectively forming a yoke 41. Above and attached to the first pole 32 at a first pole tip portion 43, is a first pole pedestal 42 abutting the ABS. In addition, a second pole pedestal 44 is attached to the second pole 38 at a second pole tip portion 45 and aligned with the first pole pedestal 42. This portion of the first and second poles 42 and 44 near the ABS is sometimes referred to as the yoke tip region 46. A write gap 36 is formed between the first and second pole pedestals 42 and 44 in the yoke tip region 46. The write gap 36 is filled with a non-magnetic material. This non-magnetic material can be either integral with (as is shown here) or separate from a first insulation layer 47 that lies below the second yoke 38 and extends from the yoke tip region 46 to the backgap portion 40. Also included in write element 28 is a conductive coil 48, formed of multiple winds, that is positioned within a dielectric medium 50 that lies above the first insulation layer 47. The configuration of the conductive coil 48 can be better understood with reference to a plan view of the read/write head 24 shown in FIG. 1D taken along line 1D--1D of FIG. 1C. As is well known to those skilled in the art, these elements operate to magnetically write data on a magnetic medium such as a magnetic disk 16.
In FIG. 1E, a view taken along line 1E--1E of FIG. 1C (i.e., perpendicular to the plane 29) further illustrates the structure of the read/write head 24 at the ABS. As can be seen from this view and in the view of FIG. 1C, the first and second pole pedestals 42 and 44 have substantially equal widths of Wp which are smaller than the width W of the first and second poles 32 and 38 in the yoke tip region 46. A critical parameter of a magnetic write element is a trackwidth defined by the geometries at the ABS. In this configuration, the trackwidth of the write element 28 is substantially equal to the width Wp. An inductive write head such as that shown in FIGS. 1C-1E operates by passing a writing current through the conductive coil 48.
Because of the magnetic properties of the yoke 41, a magnetic flux is induced in the first and second poles 32 and 38 by write currents in coil 48. The more winds between the first and second poles 42 and 44, the larger the magnetic flux that can be induced. The write gap 36 allows the magnetic flux to fringe out from the yoke 41 (thus forming a fringing gap field) and to cross a magnetic recording medium that is placed near the ABS. In this way, the write element performance is directly driven by the strength of this gap field. Thus, with a particular current, more winds results in a higher write element performance due to higher magnetic flux.
More winds in the conductive coil 48 could be included between the first and second poles by increasing the yoke length YL. Unfortunately, the recording speed is inversely related to the yoke length YL. In particular, as shown in FIG. 1F, increasing yoke length increases flux rise time, i.e., the time that it takes the magnetic flux to be generated in the poles by the writing current. The higher the flux rise time, the slower the write element can record data on a magnetic media (i.e., a lower data rate). As shown by the graph of FIG. 1F, with increasing yoke length YL, the flux rise time increases thereby decreasing recording speed of the write element.
Again referring to FIG. 1C, another way that more winds could be included in the write element could be forming additional winds in one or more additional conductive coils (not shown) above the conductive coil 48. However, this increases the stack height SH of the write element (i.e., causes a higher topography). Unfortunately, the reliability of the write element is inversely related to the stack height SH. For example, with higher topography the formation of the second pole, such as by sputtering or plating, can lead to undesirable material properties.
Another problem which increases with increasing stack height is cracking of the write element due to thermal expansion and thermal coefficient mismatch. For example, when adjacent insulation layers are formed of different materials that have different thermal coefficients, during heating the two materials may expand at different rates. When the stack height increases, the attendant geometries result in increasing likelihood of separation between the second pole 38 and the second pole pedestal 44. Regardless of the mechanism of reduced reliability, this results in undesirable lower production yield.
Alternatively, a larger writing current can be used with fewer winds to achieve the same performance. Unfortunately, however, higher current can cause higher heat levels, thus increasing problems associated with higher temperature operation. Thus, in design of write elements, tradeoffs are made between the number of winds, yoke length, and write current strength to achieve desired writing performance.
Accordingly, what is desired is an easily fabricated, reliable write element that exhibits a faster flux rise time while minimizing heat problems due to the writing current. In particular, a write element that accommodates a larger number of conductive coil winds for a given yoke length and stack height is needed.